Tributes to the victims of the Columbine school shooting 10 years ago began Sunday evening with a candlelight vigil at the native Colorado stone monument in neighboring Clement Park. Colorado Gov. Bill Ritter ordered flags to fly at half-staff Monday. A formal commemoration begins at 5 p.m. Monday at the Clement Park Amphitheater.

After the tragedy, police across the country developed "active-shooter" training. It calls for responding officers to rush toward gunfire and step over bodies and bleeding victims, if necessary, to stop the gunman the active shooter first.

They weren't goths or loners. The two teenagers who killed 13 people and themselves at suburban Denver's Columbine High School 10 years ago next week weren't in the "Trenchcoat Mafia," disaffected videogamers who wore cowboy dusters. The killings ignited a national debate over bullying, but the record now shows Eric Harris and Dylan Klebold hadn't been bullied in fact, they had bragged in diaries about picking on freshmen and "fags."